When carrying out chemical-mechanical polishing to form wiring of metal, such as copper, on semiconductor devices, the occurrence of defects known as fangs (or seams) after the polishing has been a problem in the past. In order to prevent the defects from occurring, polishing compositions such as those disclosed in Patent Documents 1 to 5 have been developed.
Plugs (contact plugs) and pads (contact pads) of semiconductor devices are formed from polysilicon (polycrystalline silicon) by chemical-mechanical polishing. When forming the plugs or pads, it is generally necessary to simultaneously polish not only parts made of polysilicon, but also parts made of silicon oxide or silicon nitride that are provided around the plugs or pads. In such cases, defects known as edge over erosion (hereinafter called EOE) may occur after the polishing in addition to fangs occurred as is the case with when forming metal wiring. It is thought that the occurrence of fangs and EOE is caused by the fact that while polysilicon parts are hydrophobic, silicon oxide parts or silicon nitride parts are hydrophilic. A fang as used herein refers to a phenomenon in which localized erosion is occurred at a boundary between a polysilicon part and a silicon oxide part or a silicon nitride part, and this is seen in particular on both sides of a relatively wide polysilicon part. EOE as used herein refers to a phenomenon in which localized erosion is occurred on both sides of a region in which relatively narrow polysilicon parts are aligned with little space therebetween. In addition to fangs and EOE, the problem of dishing, that is, dish shaped recesses, occurs due to the upper surface of a polysilicon part being lowered by excessive polishing and removal of the polysilicon part. Even when the polishing compositions disclosed in Patent Documents 1 to 5 are used, it is difficult to prevent the occurrence of defects such as fangs, EOE, and dishing during the formation of plugs or pads made of polysilicon.